RR Lyrae Variables as Tracers of the Galactic Bulge Kinematic Structure
RR Lyrae Variables as Tracers of the Galactic Bulge Kinematic Structure
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DOI：
10.3390/universe8040206
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发表时间：
2022-03
期刊：
影响因子：
2.9
通讯作者：
A. Kunder
中科院分区：
文献类型：
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作者：
A. Kunder
天琴座RR型恒星被认为是宇宙中最古老的恒星之一。此外，它们是少数几个可以可靠推断距离的古老天体之一。因此，这些恒星是存在于银河系内部的最古老结构的绝佳示踪剂。虽然银河系内部被认为是银河系中最古老的结构隐藏的地方，但由于高度灭绝和拥挤，它也是一个众所周知的难以研究的区域。在这里，我将总结一下如何使用天琴座RR型恒星来获得银河系内部更完整的图像。特别是，最近，一个大样本的RR天琴座星星运动通过空间已经获得，并比较年轻，更富金属的恒星在凸起/酒吧。可以看出，天琴座RR星系内部的星星运动学因各种银河成分的混合而变得复杂。在只分离出那些局限于隆起的RR型天琴座恒星后，这些恒星的子样本具有较慢的旋转速度，并且比主要的酒吧/隆起更少。奇怪的是，这两个子样品之间没有明显的金属含量[Fe/H]差异。当讨论导致内星系和银河棒/凸起形成的过程时，需要适当地考虑内星系中古老的贫金属恒星。
RR Lyrae stars are recognized as some of the oldest stars in the Universe. In addition, they are some of the few old celestial objects for which distances can be reliably inferred. As such, these stars are excellent tracers of the oldest structures that exist in the inner Galaxy. Although the inner Galaxy is where the oldest structures in the Milky Way are thought to be hidden, it is also a region notoriously difficult to study due to high extinction and crowding. Here, I will summarize how RR Lyrae stars have been used to obtain a more complete picture of the inner Galaxy. In particular, recently, a large sample of RR Lyrae star motions through space have been obtained and compared to younger, more metal-rich stars in the bulge/bar. It is seen that the inner Galaxy RR Lyrae star kinematics are complicated by a mix of a variety of Galactic components. After isolating only those RR Lyrae stars that are confined to the bulge, a subsample of these stars have slower rotation and are less barred than the dominant bar/bulge. Curiously, there is no discernible metallicity [Fe/H] difference between these two subsamples. Old, metal-poor stars in the inner Galaxy need to be properly accounted for when discussing processes that gave rise to the formation of the inner Galaxy and the Galactic bar/bulge.